The present invention generally refers to a composite section for doors, windows or facades, and in particular to a heat-insulated composite section of a type including metal rail sections and at least one insulating rod, preferably made of plastic material, positioned between the rail sections and connected to the rail sections along the longitudinal edges.
It is known to secure the insulating rods along the longitudinal edges through force-fitting engagement in undercut grooves of the rail sections by forming a metal web. By this type of engagement alone, the friction pairing between the insulating rod and the rail sections results in a resistance to longitudinal displacement between the rail sections which could be augmented through further measures such as a coating that increases friction, serrated groove surfaces or provision of at least one toothed wire placed between the attached metal web and the insulating rod.
The resistance to longitudinal displacement of the composite section results in a higher, effective moment of inertia for static loads in conjunction with bar-post-constructions employed in metal structures.
Other composite profiled systems describe the securement of the insulating rod by means of mechanical spreaders or bloating foams.
The force-fitting connection or positive engagement in longitudinal direction between the insulating rods and the rail sections of the composite sections is capable of absorbing increased forces of displacement when subject to static or dynamic loads caused e.g. by wind-generated suction or pressure forces, and thus reducing flexures at static or dynamic loads in respect to the addition of individual moments of inertia of single rail sections assembled to form a composite section. This type of composite section is called "displacement-resistant" composite.
The insulating rods form between the metal rail sections a thermal partition plane by which the heat flux from one rail section to the other rail sections is limited to a minimum.
In the event the rail sections of the displacement-resistant composite section are unilaterally subjected to a temperature rise, the length expansion of the heated rail section results in a displacement force between the rail sections of the composite section to thereby cause a flexure of the composite section because of the resistance to longitudinal displacement of the composite section. Heat sources that may effect a one-sided temperature rise are e.g. temperature differences between a room inner side and the outer air (winter operation) or incident solar radiation upon the outside (summer operation) that leads to a temperature rise of the outside through absorption of solar energy. The ensuing deformation of the composite section causes always an arching toward the warmer side and impairs the function of the window or door as the frame thereof is made from a composite section.
Especially when the rail sections are relatively long, e.g. vertical frame sections of doors, flexures caused as a consequence of the one-sided heating adversely affect the tightness and the locking capability of the locks. This is true for a simple center lock or a multiple lock so that a breakdown of the locking function may be experienced.
Temperature fluctuations from 50 to 60.degree. C. as a result of incident solar radiation upon dark surfaces, may cause flexures of such an extent that even the compensation capability of sealing systems may not be sufficient to close the created gap. The flexure created by temperature differences between the outer and the inner metal rail sections of the composite section also leads to stress upon the provided lock of a door. This stress is experienced in conventional multiple-lock mechanisms at least in connection with one of the locks so that the door cannot be securely closed or opened by the key.